Fuel cells have gained in popularity and sophistication in recent years. Fuel cells conduct an electrochemical reaction of with oxygen and a fuel to produce electricity and heat. Fuel cells are similar to batteries, but they can be “recharged” while providing power, and usually operate much more cleanly than conventional hydrocarbon combustion.
Fuel cells provide a DC (direct current) voltage that may be used to power motors, lights, computers, or any number of electrical appliances. There are several different types of fuel cells, each using a different chemistry. Fuel cells are usually classified by the type of electrolyte used. The fuel cell types are generally categorized into one of five groups: proton exchange membrane (PEM) fuel cells, alkaline fuel cells (AFC), phosphoric-acid fuel cells (PAFC), solid oxide fuel cells (SOFC), and molten carbonate fuel cells (MCFC).
Many fuel cells use hydrogen as their fuel. This facilitates clean and effective electricity production with water as the only theoretical by-product. However, hydrogen is often difficult and costly to produce and store. Therefore, SOFCs are a particularly promising fuel cell type because they do not require a pure hydrogen source for fuel. While SOFCs are operable with hydrogen, they may also use a variety of other fuels. SOFCs often operate on fuels that are less expensive and more readily available than hydrogen, such as hydrocarbons and alcohols.
Nevertheless, several challenges remain in the development of commercially viable solid oxide fuel cells for powering consumer electronics. SOFCs operate in a temperature range (400-1000° C.) that precludes sealing materials such as rubber or plastic from being used between the various fuel cell system components.
Consequently, seals for various SOFC system components have been made of mica, glass, or glass ceramics. These seals are used to prevent leaks of fuel and by-products from the fuel cell system, even at high operating temperatures.
However, mica has very limited compliance characteristics, which often result in a poor seal. Glass is even less compliant than mica, which often results in cracked seals and/or damaged fuel cell system components.
Additionally, the differences in the coefficients of thermal expansion between the seals and the fuel cell system components make it very difficult to create and maintain effective seals in solid oxide and other high-temperature fuel cell applications. Again, this is due to the high operating temperatures of the fuel cell system